A mass air conveying system is disclosed in my U.S. Pat. No. 4,456,406. In this apparatus, air is supplied by a plenum through a jet board forming the top surface of the conveyor. The sidewalls of the conveyor can be either open or closed, and a cover is provided having widely spaced apertures to form high pressure areas therebetween to create air barriers for the containers to maintain them in a loose separated condition as they move through the conveyor. In addition, the top cover prevents the containers from tipping over.
My U.S. Pat. No. 4,561,806 is directed to a vertical single filer conveyor system which also supplies air to the surface through a jet board by means of a plenum thereunder. The single filer has converging closed sidewalls and a top cover with widely spaced apertures for the same purpose as described above. Acceleration jets are also provided for increasing the speed of the containers as they are brought into single file.
Air conveyors and air single filers have substantial advantages over mechanical conveyors and single filers in that much higher speed of handling of the containers is possible. However, one of the disadvantages is that in order to create the high pressure within the conveyor or single filer it is necessary to have a top cover which is located just above the top of the containers so that they will not tip over and to create sufficiently high air pressure to cause proper separation of the articles. Because of this, each system is set up to handle containers of a particular height. When it is necessary to use the system with containers of a different height, the cover on the table must be either raised or lowered. This results in substantial downtime and, of course, increases labor costs. Furthermore, if containers jam or otherwise become improperly aligned within the prior art systems, it is necessary to remove the top cover in order to reach them to remove them or correct their alignment.